[racket] (where-not ...) in Redex

On Aug 25, 2012, at 10:53 PM, Robby Findler wrote:

> On Thu, Aug 23, 2012 at 8:11 AM, Matthias Felleisen
> <matthias at ccs.neu.edu> wrote:
>> 
>> I would almost prefer the use of 'when' for 'where' and the introduction of 'unless'.
> 
> If we did this, then there could be no judgment-forms name 'when' or
> 'unless', which makes me think we shouldn't do this.

I don't understand this point at all. 


>> The type setting of 'when' could still use 'where' as the English word (and perhaps we can have a way to override it).
>> 
>> I am not sure how to type set 'unless' other than by providing a the negative operator as an argument !=
> 
> Using \neq{} seems right to me.

What if you want \not\in or \not\subtype and such? 

-- Matthias




> 
> Robby
> 
>> -- Matthias
>> 
>> 
>> 
>> 
>> On Aug 22, 2012, at 3:47 PM, Asumu Takikawa wrote:
>> 
>>> Hi all,
>>> 
>>> Had a question/feature request for Redex. In various models, I've
>>> encountered situations where I wanted the dual behavior to the
>>> (where pattern term) clause of Redex (i.e., does term *not* match this
>>> pattern).
>>> 
>>> In the past, I've used side-conditions or where clauses with predicate
>>> metafunctions for this case. For example,
>>> (side-condition ,(not (redex-match ...)))
>>> 
>>> or
>>> 
>>> (where #f (matches this that))
>>> 
>>> Both of these have the disadvantage that it's more work to typeset.
>>> It would be convenient to have a form like
>>> (where-not pattern term)
>>> 
>>> that would typeset like the following:
>>> 
>>> where term ≠ pattern
>>> 
>>> This seems like a common enough pattern that it would be nice to support
>>> it as a built-in (and typeset) construct. Does that seem like a
>>> reasonable thing to add?
>>> 
>>> Cheers,
>>> Asumu
>>> ____________________
>>> Racket Users list:
>>> http://lists.racket-lang.org/users
>> 
>> 
>> ____________________
>>  Racket Users list:
>>  http://lists.racket-lang.org/users
>> 

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